The present invention relates to a controller for an absorption cold or hot water generating machine, and particularly, to a flow controller of a solution pump in an absorption cold or hot water generating machine.
In absorption cold/hot water generating machines of this kind, one having the arrangement as shown in FIG. 4 has conventionally been in common use. Normally, an absorption cold/hot water generating machine comprises, as shown in FIG. 4, an evaporator 1, an absorber 2, a condenser 3, a low-temperature generator 4, a high-temperature generator 5, a solution pump 6, a refrigerant pump 7, a cooling water pump 17, a solution heat exchanger 22, and a cooling tower 23, with piping 9 for connecting these components.
In the absorption cold/hot water generating machine, usually a refrigerant is sent and sprayed in the evaporator 1 by means of the refrigerant pump 7, where it evaporates, and takes heat from water sent from a load L by means of a cold/hot water pump 18, thereby producing cold water. Refrigerant vapor produced through evaporation in the evaporator 1 is absorbed, in the absorber 2, by a high-concentration solution (absorbing solution) (hereinafter referred to as the "concentrated solution") fed from the high-temperature generator 5 through the piping 9.sub.1 and 9.sub.2 and the solution heat exchanger 22 and sprayed there and the concentrated solution thus becomes a lower-concentration solution (hereinafter referred to as the "diluted solution").
The diluted solution in the absorber 2 is sent to the high-temperature generator 5 and the low-temperature generator 4 by the solution pump 6 via piping 9.sub.3 and 9.sub.4 respectively, heated in the high-temperature generator 5 and the low-temperature generator 4, respectively, and sent back to the absorber 2 via piping 9.sub.1, 9.sub.5 and 9.sub.2 in the form of the concentrated solution to continue the refrigerating cycle. Cooling water in the cooling tower 23 is circulated by the cooling water pump 17 through the absorber 2, the condenser 3 and the cooling tower 23. The solution pump 6, the refrigerant pump 7, the cooling water pump 17 and the cold/hot water pump 18 are controlled by the controller 10.
In the high-temperature generator 5, the diluted solution sent from the absorber 2 by the solution pump 6 is heated, and the refrigerant is evaporated to produce the concentrated solution which flows into the header 8. The concentrated solution returns from the header 8 through the solution heat exchanger 22 to the absorber 2. A float 19 is provided in the header 8, and a valve 19a operating in conjunction with this float is provided at an entry piping 9.sub.3 into the high-temperature generator 5. When a predetermined amount of solution is not present in the header 8, the valve 19a is controlled to the opening side so as to feed the diluted solution to the high-temperature generator 5, and when the header 8 contains a predetermined amount of solution, the valve 19a is controlled to the closing side so as to keep a constant liquid level in the high-temperature generator 5. When the valving is not completely effected by the valve 19a, the solution pump 6 is started or stopped by detecting the liquid level in the header 8 by means of electrodes 15 and 16.
The liquid level in the high-temperature generator is kept constant for the following reason. That is, when the amount of solution sent to the high-temperature generator 5 exceeds a certain level, the solution overflows and enters the piping for the refrigerant, thus contaminating the refrigerant and leading to a lower evaporation temperature of the refrigerant. When the amount of the solution is under a certain lower limit, on the contrary, a refrigerant gas is mixed into the solution piping, thus causing noise or corrosion, possibly even leading to crystallization. The amount of diluted solution fed from the absorber 2 to the high-temperature generator 5 must therefore be appropriate.
As described above, the absorption cold/hot water generating machine of the conventional arrangement does not adopt an inverter for controlling the solution pump, but controls the amount of solution by the use of a float valve comprising the float 19 and the valve 19a operating in conjunction therewith in the header 8. Upon controlling the amount of solution with the float valve, however, the squeezing or valving property of the valve 19a is rough and, thus, when a load is small, a frequent start and stop operation of the solution pump 6 is needed, and circulating flow rate of the solution tends to be excessive, resulting in poor efficiency of the machine.
In addition, the size of the float 19 tends to be large, because the valve 19a must be driven by floating force of the float 19. This results in a larger width of the header, leading to a larger exterior size of the absorption cold/hot water generating machine.